Merck Bolsters Oncology Arsenal Against Keytruda's 2028 Patent Cliff—Pipeline Could Be the Game Changer

Merck faces a critical juncture as its star immunotherapy drug Keytruda approaches patent expiration in 2028, yet the pharmaceutical giant is aggressively positioning itself to weather this transition. Keytruda remains the financial backbone of the company, generating $23.3 billion in sales during the first nine months of 2025—an 8% increase year-over-year—and accounting for over half of Merck’s total pharmaceutical revenues. The impending loss of exclusivity (LOE) has forced the company to rethink its growth strategy, shifting focus toward newly commercialized medications and an expanding portfolio of late-stage development candidates.

Building a Fortress: Merck’s Accelerated Pipeline Expansion

Since 2021, Merck has transformed its late-stage development portfolio, nearly tripling the number of Phase III candidates through organic advancement and strategic acquisitions. This aggressive expansion sets the stage for approximately 20 new product launches over the coming years, many positioned as potential blockbusters capable of replacing Keytruda’s revenue contribution.

Among the flagship launches, two drugs stand out as central to Merck’s post-Keytruda strategy: Capvaxive, a 21-valent pneumococcal conjugate vaccine, and Winrevair, a pulmonary arterial hypertension treatment. Both have demonstrated strong commercial momentum since hitting the market. Additionally, Merck’s respiratory syncytial virus (RSV) antibody therapy, Enflonsia (clesrovimab), secured U.S. approval in June 2025 and is under regulatory review in Europe.

The pipeline depth extends across multiple therapeutic areas. Late-stage candidates include enlicitide decanoate (MK-0616), an oral PCSK9 inhibitor targeting hypercholesterolemia; tulisokibart, a TL1A inhibitor for ulcerative colitis; bomedemstat (MK-3543) for hematologic and hematopoietic disorders; and nemtabrutinib (MK-1026) for various hematological malignancies. Merck’s partnership with Daiichi Sankyo on three DXd antibody-drug conjugates—patritumab deruxtecan, ifinatamab deruxtecan, and raludotatug deruxtecan—further diversifies cancer treatment options across multiple tumor types.

Strategic M&A: Accelerating Time to Market

To fortify its pipeline, Merck has embarked on a multi-billion-dollar acquisition spree. The recent agreement to acquire Cidara Therapeutics for $9.2 billion adds CD388, a late-stage antiviral candidate for influenza prevention. Earlier in the year, the $10 billion acquisition of Verona Pharma brought Ohtuvayre into Merck’s commercial arsenal—a first-in-class treatment for chronic obstructive pulmonary disease maintenance therapy.

International partnerships have also accelerated pipeline depth, with substantial investments in Chinese biotech firms including Hansoh Pharma, LaNova Medicines, and Hengrui Pharma, enabling Merck to access innovative candidates across diverse therapeutic domains.

The Competitive Landscape: PD-L1 Market Remains Crowded

Keytruda’s dominance faces serious headwinds from competing PD-L1 inhibitors. Bristol Myers Squibb’s Opdivo generated $7.35 billion in sales during the first nine months of 2025 (up 8% year-over-year), approved across multiple malignancy types including lung, melanoma, and renal cancers. Roche’s Tecentriq, the company’s leading immuno-oncology asset, recorded CHF 2.61 billion in sales during the same period, while AstraZeneca’s Imfinzi demonstrated the strongest momentum with $4.32 billion in revenues—up 25%—boosted by expanded use in lung and hepatic cancer indications.

This competitive intensity underscores why Merck’s diversification strategy becomes essential; relying solely on immunotherapy could leave the company vulnerable as the patent landscape shifts.

Valuation and Market Positioning

From a valuation perspective, Merck appears undervalued relative to peers. The stock trades at a forward P/E ratio of 11.22x, considerably below the industry average of 16.59x and below its own five-year mean of 12.51x. Year-to-date performance has lagged, with shares declining 0.4% while the broader pharmaceutical industry rallied 13.6% and the S&P 500 advanced further.

Analyst expectations reflect mixed sentiment. The Zacks Consensus Estimate for 2025 EPS stands at $8.98 per share (revised upward from $8.94), while 2026 EPS projections have contracted to $8.81 from $9.46 over the past 60 days—suggesting some caution about near-term growth trajectories. Merck currently holds a Zacks Rank of #3 (Hold), reflecting neutral positioning amid the uncertainty surrounding Keytruda’s LOE timeline and pipeline execution risk.

Will the Pipeline Deliver?

The central question remains whether Merck’s newly launched products and promising candidates can adequately offset Keytruda’s revenue decline when patent exclusivity ends. The company’s aggressive investment in both organic pipeline development and transformative acquisitions demonstrates management’s commitment to navigating this critical transition. However, execution risk persists—successful launches, regulatory approvals, and market adoption will ultimately determine whether Merck emerges from the 2028 patent cliff as a diversified growth story or faces significant revenue compression.